This application claims the priority of Korean Patent Application No. 10-2005-0089970, filed on Sep. 27, 2005 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a carboxylic ester dispersant and a sulfide phosphor paste composition comprising the same. More particularly, the present invention pertains to a carboxylic ester dispersant which has a tail structure including hydrophilic and hydrophobic blocks to prevent oxidation by a solvent and to improve dispersibility, and a sulfide phosphor paste composition comprising the same.
2. Description of the Related Art
Recently, a liquid crystal display, a plasma display panel, an electroluminescent display, a field emission display, and a vacuum fluorescent display have been developed and extensively used as a flat panel display (FPD) to replace the conventional cathode ray tube (CRT). These displays all have a phosphor film, and luminescent properties of the displays depend on physical properties of the phosphor film.
A sulfide phosphor, such as SrGa2S4, is extensively used in the field emission display and cathodoluminescence display fields. A phosphor paste composition is uniformly applied on a predetermined supporter and then dried to produce a phosphor used as a phosphor film of a display. A sulfide phosphor paste composition consists mostly of a mixture of a solvent, a binder, and a sulfide phosphor, and may further include a dispersant to improve the dispersibility of the phosphor.
The sulfide phosphor paste tends to react with moisture or be chemically unstable in an organic solvent, such as ethyl cellulose, terpineol, and butyl carbitol acetate (BCA), used to produce the phosphor paste. Some components of the sulfide phosphor paste composition may be completely dissolved in the solvent, such as ethyl cellulose. In this case, when it is used as the phosphor film for a display, the luminescent properties of the display may deteriorate.
Furthermore, if the viscosity reduction effect owing to the dispersant is insufficient in the sulfide phosphor, the use of a relatively small amount of phosphor is necessary to avoid undesirable increases in viscosity. On the other hand, an increase in the loading amount of the phosphor will cause an increase in viscosity, thereby making uniform formation of the phosphor film difficult. Thus, insufficient viscosity reduction has a detrimental impact on processability and/or productivity.